A Report on Green Energy & Technologies

1. Seminar Report 2012
GREEN
ENERGY
A Report submitted of the
requirements for the Seminar
B.Tech, 2009-13 Batch
Civil Engineering
VII Semester
KIET Ghaziabad
2012
Date: 20/11/12
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CONTENTS
1. Green Energy: An Overview
2. Biomass Energy
2.1. Introduction
2.2. The Future Role of Biomass
2.3. Implementation of Biomass Energy Systems
2.4. Conclusions
3. Wind Energy
3.1. Introduction
3.2. Economics of Wind Energy
3.3. Conclusions
4. Solar Energy
4.1. Solar Photovoltaic
4.2. Solar Thermal Systems
5. Hydropower
5.1. Introduction
5.2. Capacity and Potential
5.3. Small Hydro
5.4. Environmental and Social Impacts
5.5. Conclusions
6. Geothermal Energy
6.1. Introduction
6.2. Capacity and Potential
6.3. Environmental Impacts
6.4. Conclusions
7. Renewable Energy System Cost and Performance
Recent progress in Renewable Energy System Cost and Performance
8. Conclusions
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SUMMARY
Conventional energy sources based on oil, coal, and natural gas have proven to be highly
effective drivers of economic progress, but at the same time damaging to the environment
and to human health. Furthermore, they tend to be cyclical in nature, due to the effects of
oligopoly in production and distribution. These traditional fossil fuel-based energy sources
are facing increasing pressure on a host of environmental fronts, with perhaps the most
serious challenge confronting the future use of coal being the Kyoto Protocol greenhouse
gas (GHG) reduction targets.
The potential of renewable energy sources is enormous as they can in principle meet many
times the world’s energy demand. Renewable energy sources such as biomass, wind, solar,
hydropower, and geothermal can provide sustainable energy services, based on the use of
routinely available, indigenous resources. A transition to renewables-based energy systems
is looking increasingly likely as their costs decline while the price of oil and gas continue to
fluctuate. In the past 30 years solar and wind power systems have experienced rapid sales
growth, declining capital costs and costs of electricity generated, and have continued to
improve their performance characteristics. In fact, fossil fuel and renewable energy prices,
and social and environmental costs are heading in opposite directions and the economic
and policy mechanisms needed to support the widespread dissemination and sustainable
markets for renewable energy systems are rapidly evolving. It is becoming clear that future
growth in the energy sector will be primarily in the new regime of renewable energy, and
to some extent natural gas-based systems, not in conventional oil and coal sources. Because
of these developments market opportunity now Exists to both innovate and to take
advantage of emerging markets to promote renewable energy technologies, with the
additional assistance of governmental and popular sentiment. The development and use of
renewable energy sources can enhance diversity in energy supply Markets contribute to
securing long term sustainable energy supplies, help reduce local and global atmospheric
emissions, and provide commercially attractive options to meet specific energy service
needs, particularly in developing countries and rural areas helping to create new
employment opportunities there.
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OVERVIEW
What is Green Energy?
Greenenergy uses energy sources that are continually replenished by
nature—the sun, the wind, water, the Earth’s heat, and plants. Green energy
technologies turn these fuels into usable forms of energy—most often
electricity, but also heat, chemicals, or mechanical power.
Why Use Green Energy?
Todaywe primarily use fossil fuels to heat and power our homes and fuel our
cars. It’s convenient to use coal, oil, and natural gas for meeting our energy
needs, but we have a limited supply of these fuels on the Earth. We’re using
them much more rapidly than they are being created. Eventually, they will run
out. And because of safety concerns and waste disposal problems, the United
States will retire much of its nuclear capacity by 2020. In the meantime, the
nation’s energy needs are expected to grow by 33 percent during the next 20
years. This Green energy can help fill the gap.
Even if we had an unlimited supply of fossil fuels, using Green energy is better
for the environment. We often call Green energy technologies
“Clean”&“Renewable”because they produce few if any pollutants. Burning
fossil fuels, however, sends greenhouse gases into the atmosphere, trapping
the sun’s heat and contributing to global warming. Climatescientists generally
agree that the Earth’s average temperature has risen in the past century. If
this trend continues, sea levels will rise, and scientists predict that floods, heat
waves, droughts, and other extremeweather conditions could occur more
often.
Green Energy is plentiful, and the technologies are improving all the time.
There are many ways to use renewable energy. Most of us already use
renewable energy in our daily lives
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Biomass Energy
2.1. Introduction
Biomass is the term used for all organic material originating from plants (including algae),
trees and crops and is essentially the collection and storage of the sun’s energy through
photosynthesis. Biomass energy, or bioenergy, is the conversion of biomass into useful
forms of energy such as heat, electricity and liquid fuels.
Biomass for bioenergy comes either directly from the land, as dedicated energy crops, or
from residues generated in the processing of crops for food or other products such as pulp
and paper from the wood industry. Another important contribution is from post consumer
residue streams such as construction and demolition wood, pallets used in transportation,
and the clean fraction of municipal solid waste (MSW). The biomass to bioenergy system
can be considered as the management of flow of solar generated materials, food, and fiber
in our society. Not all biomass is directly used to produce energy but rather it can be
converted into intermediate energy carriers called biofuels. This includes charcoal (higher
energy density solid fuel), ethanol (liquid fuel), or producer-gas (from gasification of
biomass).
Biomass was the first energy source harnessed by humans, and for nearly all of human
history, wood has been our dominant energy source. Only during the last century, with the
development of efficient techniques to extract and burn fossil fuels, have coal, oil, and
natural gas, replaced wood as the industrialized world’s primary fuel.. The precise amount
is uncertain because the majority is used non-commercially in developing countries.
Biomass is usually not considered a modern energy source, given the role that it has played,
and continues to play, in most developing countries. In developing countries it still
accounts for an estimated one third of primary energy use while in the poorest up to 90%
of all energy is supplied by biomass. Over two billion people cook by direct combustion of
biomass, and such traditional uses typically involve the inefficient use of biomass fuels,
largely from low cost sources such as natural forests, which can further contribute to
deforestation and environmental degradation. The direct combustion of biomass fuels, as
used in developing countries today for domestic cooking and heating, has been called “the
poor man’s oil” ranking at the bottom of the ladder of preferred energy carriers where gas
and electricity are at the top.
The picture of biomass utilization in developing countries is sharply contrasted by that in
industrialized countries. On average, biomass accounts for 3 percent or 4 percent of total
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energy use in the latter, although where policies supportive of biomass use are in place, e.g.
in Austria, Sweden, and Finland, the biomass contribution reaches 12, 18, and 23 percent
respectively. Most biomass in industrialized countries is converted into electricity and
process heat in cogeneration systems (combined heat and power production) at industrial
sites or at municipal district heating facilities. This enables a greater variety of energy
services to be derived from the biomass which are much cleaner and use the available
biomass resources more efficiently than is typical in developing countries.
Biomass energy has the potential to be “modernized” worldwide, that is produced and
converted efficiently and cost-competitively into more convenient forms such as gases,
liquids, or electricity. A variety of technologies can convert solid biomass into clean,
convenient energy carriers over a range of scales from household/village to large
industrial. Some of these technologies are commercially available today while others are
still in the development and demonstration stages. If widely implemented, such
technologies could enable biomass energy to play a much more significant role in the future
than it does today, especially in developing countries.
2.2. The Future Role of Biomass
Modernized biomass energy is projected to play a major role in the future global energy
supply. This is being driven not so much by the depletion of fossil fuels, which has ceased to
be a defining issue with the discovery of new oil and gas reserves and the large existing
coal resources, but rather by the recognized threat of global climate change, caused largely
by the burning of fossil fuels. Its carbon neutrality (when produced sustainably) and its
relatively even geographical distribution coupled with the expected growth in energy
demand in developing 12 countries, where affordable alternatives are not often available,
make it a promising energy source in many regions of the world for the 21st century.
Most households in developing countries that use biomass fuels today do so either because
it is available at low (or zero) financial cost or because they lack access to or cannot afford
higher quality fuels. As incomes rise, preferences tend to shift away from biomass. For
example, in the case of cooking, consumer preferences shift with increasing income from
dung to crop residues, fuel wood, coal, charcoal, kerosene, liquefied petroleum gas, natural
gas, and electricity (the well-knownhousehold energy ladder). This shift away from
biomass energy as incomes rise is associated with the quality of the energy carrier used
rather than with the primary energy source itself. If biomass energy is instead modernized,
then wider use is conceivable along with benefits such as reduced indoor air pollution. For
example, in household cooking gaseous or liquid cooking fuels can be used far more
efficiently and conveniently, reaching many more families and emitting far fewer toxic
pollutants, than solid fuels.
Estimates of the technical potential of biomass energy are much larger than the present
world energy consumption. If agriculture is modernized up to reasonable standards in
various regions of the world, several billions of hectares may be available for biomass
energy production well into this century. This land would comprise degraded and
unproductive lands or excess cropland, and preserve the world’s nature areas and quality
cropland. Table 1 gives a summary of the potential contribution of biomass to the worlds
energy supply according to a number of studies and influential organizations. Although the
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percentile contribution of biomass varies considerably, depending on the expected future
energy demand, the absolute potential contributions of biomass in the long term is high,
from about 100 to 300 EJ per year.
2.3. Implementation of Biomass Energy Systems
Raw biomass has several disadvantages as an energy source. It is bulky with a low energy
density and direct combustion is generally highly inefficient (other than advanced domestic
heaters) producing high levels of indoor and outdoor air pollution. The goal of modernized
biomass energy is to increase the fuel’s energy density while decreasing its emissions
during production and use. Modernizing biomass energy production however faces a
variety of challenges that must be adequately addressed and dealt with before the
widespread implementation of bioenergy systems can occur. These issues include technical
problems (just discussed), resource availability, environmental impacts, and economic
feasibility.
2.4. Conclusions
Biomass is one of the renewable energy sources that is capable of making a large
contribution to the world’s future energy supply. Land availability for biomass production
should not be a bottleneck, provided it is combined with modernization of conventional
agricultural production.
Recent evaluations indicate that even if land surfaces of 400-700 million hectares were
used for biomass production for energy about halfway the next century, this could be done
without conflicting with other land-use functions and nature preservation. Partially this
can be obtained by better agricultural practices, partially by making use of huge areas of
unproductive degraded lands. Latin America, Africa, Asia and to a lesser extent Eastern
Europe and North America represent a large potential for biomass production. The forms
in which biomass can be used for energy are diverse and optimal resources, technologies
and entire systems will be shaped by local conditions, both physical and socioeconomic.
Perennial crops in particular may offer cheap and productive biomass production
systems with low or positive environmental impacts. Technical improvement and
optimized production systems along with multifunctional land-use could bring biomass
close to the costs of fossil fuels.
A key issue for bioenergy is that its use must be modernized to fit into a sustainable
development. Conversion of biomass to energy carriers like electricity and transportation
fuels will give biomass a commercial value and provide income for local rural economies. In
order to obtain such a situation it is essential that biomass markets and necessary
infrastructure are built up, key conversion technologies like IGCC technology and advanced
fuel production systems for methanol, hydrogen and ethanol are demonstrated and
commercialized, and that much more experience is gained with biomass production
systems in a wide variety of contexts. Although the actual role of bioenergy will depend on
its competitiveness versus fossil fuels and agricultural policies, it seems realistic to expect
that the current contribution of bioenergy will increase during this century
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Wind Energy
3.1. Introduction
Wind has considerable potential as a global clean energy source, being both widely
available, though diffuse, and producing no pollution during power generation. Wind
energy has been one of humanity’s primary energy sources for transporting goods, milling
grain, and pumping water for several millennia. From windmills used in China, India and
Persia over 2000 years ago to the generation of electricity in the early 20th century in
Europe and North America wind energy has played an important part in our recorded
history. As industrialization took place in Europe and then in America, wind power
generation declined, first gradually as the use of petroleum and coal, both cheaper and
more reliable energy sources, became widespread, and then more sharply as power
transmission lines were extended into most rural areas of industrialized countries. The
oil crises of the 70’s, however, triggered renewed interest in wind energy technology for
grid connected electricity production, water pumping, and power supply in remote areas,
promoting the industry’s rebirth.
This impetus prompted countries; notably Denmark and the United States, to establish
Government research and development (R&D) programs to improve wind turbine
technology. In conjunction with private industry research this lead to a reemergence in the
1980’s of wind energy in the United States and Europe, when the first modern grid-
connected wind turbines were installed. In the 1990’s this development accelerated, with
wind becoming the fastest growing energy technology in the world developing into a
commercially competitive global power generation industry. While in 1990 only about
2000 MW of grid-connected wind power was in operation worldwide by 1999 this figure
had surpassed 10,000 MW, not including the over one million water-pumping wind
turbines located in remote areas.
Since 1990 the average annual growth rate in world wind generating capacity has been 24
percent, with rates of over 30 percent in the last two years. Today there is more than
13,000 MW of installed wind power, double the capacity that was in place just three years
earlier. This dramatic growth rate in wind power has created one of the most rapidly
expanding industries in the world, with sales of roughly $2 billion in 1998, and predictions
of tenfold growth over the next decade. Most 2000 forecasts for installed capacity are being
quickly eclipsed with wind power having already passed the 10,000 MW mark in early
1999.
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3.2. Economics of Wind Energy
Larger turbines, more efficient manufacturing, and careful siting of wind machines have
brought wind power costs down precipitously from $2600 per kilowatt in 1981 to $800
per kilowatt in 1998. New wind farms in some areas have now reached economic parity
with new coal-based power plants. And as the technology continues to improve, further
cost declines are projected, In addition to being cost-competitive and environmentally
sound wind energy has several additional advantages over conventional fossil fuel power
plants and even other renewable energy sources. First it is modular: that is, the generating
capacity of wind farms can easily be expanded since new turbines can be quickly
manufactured and installed, not true for either coal fired or nuclear power plants.
Furthermore, a repair to one wind turbine does not effect the power production of all the
others. Second, the energy generated by wind turbines can pay for the materials used to
make them in as short as 3 - 4 months for good wind sites. Thirdly, duringnormal operation
they produce no emissions. One estimate of wind energy potential to reduce
CO2 emissions predicts that a 10 percent contribution of wind energy to the world’s
electricity demand by 2025 would prevent the emission of 1.4 Gton/year of CO2. Despite
these advantages wind’s biggest drawback continues to be its intermittence and mismatch
with power demand.
3.3. Conclusions
For the first time, we are seeing one of the emerging renewable energy generating
options—wind power—in a position to compete with the generation technologies of the
last century. A variety of players are engaged in pushing forward wind projects worldwide.
Enron Wind Corporation acquired German turbine manufacturer Tacke; NEG Micon of
Denmark has built manufacturing facilities in the U.S., Vistas of Denmark has built factories
in Spain and India and many manufacturers have developed joint ventures in various
countries around the world. This globalization trend is likely to continue as financial
institutions are beginning to view the wind industry as a promising investment
opportunity. As more countries are added to the wind energy roster, uneven development
focusing on a half-dozen key markets will most likely be replaced by more balanced
growth. During the next couple of years, large-scale projects are expected to be
developed in Egypt, Nicaragua, Costa Rica, Brazil, Turkey, Philippines, and several other
countries, totaling thousands of MW of new installed capacity, and expanding the number
ofcountries using their wind resources.
Yet, as land constraints, lower average wind speeds in future projects, as well as possibly
lower energy prices impact the economics of future projects wind penetration will likely
begin to saturate and the growth rates quoted above slow. This trend may be offset,
however, by the use of larger, more efficient turbines, where the average size per turbine
installed has already increased from 630 kW in 1997 to megawatt size systems in 1999,
allowing operators to lower generation costs. The increase in capacity factor (annual
energy output/output based on full time operation at rated power) from 20-25 % also
reflects improved efficiency and siting of projects. In addition, the future development of
offshore wind farms will open up new frontiers in wind energy development.
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The issue of wind power opportunity is likely to become increasingly relevant in
determining its future use in world electricity supply. Understanding wind prospects is
important in expected “normal” energy futures as well as for possible exceptional ones. As
wind turbine costs decline and their performance improves, the extent to which wind
resources, transmission and distribution networks, and market forces complement or
offset these improvements becomes all the more pertinent for near and mid-term
electricity supply. If these additional factors have little influence, then improved wind
technologies may enjoy fairly rapid penetration into electricity markets. Wind power may
find itself still a marginal source ofelectric power supply.
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Solar Energy
There are two basic categories of technologies that convert sunlight into useful forms of
energy, aside from biomass-based systems that do this in a broader sense by using
photosynthesis from plants as an intermediate step. First, solar photovoltaic (PV) modules
convert sunlight directly into electricity. Second, solar thermal power systems use focused
solar radiation to produce steam, which is then used to turn a turbine producing electricity.
The following provides a brief overview of these technologies, along with their current
commercial status.
4.1. Solar Photovoltaics
Solar PV modules are solid-state semiconductor devices with no moving parts that convert
sunlight into direct-current electricity. The basic principle underlying the operation of PV
modules dates back more than 150 years, but significant development really began
following Bell Labs’ invention of the silicon solar cell in 1954. The first major application of
PV technology was to power satellites in the late 1950s, and this was an application where
simplicity and reliability were paramount and cost was a secondary concern. Since that
time, enormous progress has been made in PV performance and cost reduction, driven at
first by the U.S. space 35 program’s needs and more recently through private/public sector
collaborative efforts in the U.S., Europe, and Japan.
At present, annual global PV module production is over 150 MW, which translates into a
more than $1 billion/year business. In addition to the ongoing use of PV technologies in
space, their present-day cost and performance also make them suitable for many grid-
isolated and even grid connected applications in both developed and developing parts of
the world. PV technologies are potentially so useful that as their comparatively high initial
cost is brought down another order of magnitude, it is very easy to imagine them becoming
nearly ubiquitous late in the 21stcentury. PV systems would then likely be employed on
many scales in vastly differing environments, from microscopic cells to 100 MW or larger
‘central station’ generating plants covering square kilometers on the earth’s surface and in
space. The technical and economic driving forces that favor the use of PV technologies in
these widely diverse applications will be equally diverse. However, common among them
will be the durability, high efficiency, quiet operation, and lack of moving parts that PV
systems offer, and the fact that these attributes combine to provide a power source with
minimum maintenance and unmatched reliability.
PV system cost and performance have been steadily improving in recent years.
The cost of electricity produced from PV systems is still higher than from most other
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competing technologies, at about 30 cents per kWh, but these costs are expected to
continue to decline steadily.. These potential reductions in cost, combined with the
simplicity, versatility, reliability, and low environmental impact of PV systems, should help
them to become increasingly important sources of economical premium-quality power
over the next 20 to 30 years.
4.2. Solar Thermal Systems
Solar thermal power systems use various techniques to focus sunlight to heat an
intermediary fluid, known as heat transfer fluid that then is used to generate steam. The
steam is then used in a conventional steam turbine to generate electricity. At present, there
are three solar thermal power systems currently being developed: parabolic troughs,
power towers, and dish/engine systems.
Because these technologies involve a thermal intermediary, they can be readily hybridized
with fossil fuels and in some cases adapted to utilize thermal storage. The primary
advantage of hybridization and thermal storage is that the technologies can provide
dispatchable power and operate during periods when solar energy is not available.
Hybridization and thermal storage can enhance the economic value of the electricity
produced, and reduce its average cost.
Parabolic trough solar thermal systemsare commercially available. These systems use
parabolic trough-shaped mirrors to focus sunlight on thermally efficient receiver tubes that
contain a heat transfer fluid. This fluid is heated to about 390° C. (734° F) and pumped
through a series of heat exchangers to produce superheated steam that powers a
conventional turbine generator to produce electricity. Nine of these parabolic trough
systems, built in 1980s, are currently generating 354 MW in Southern California. These
systems, sized between 14 and 80 MW, are hybridized with up to 25 percent natural gas in
order to provide dispatchable power when solar energy is not available.
Dish/engine solar thermal systems, currently in the prototype phase, use an array of
parabolic dish-shaped mirrors to focus solar energy onto a receiver located at the focal
point of the dish.
Fluid in the receiver is heated to 750° C (1,382° F) and used to generate electricity in a
small engine attached to the receiver. Engines currently under consideration include
Stirling and Brayton-cycle engines. Several prototype dish/engine systems, ranging in size
from 7 to 25 kW, have been deployed in various locations in the U.S. and elsewhere. High
optical efficiency and low startup losses make dish/engine systems the most efficient of all
solar technologies, with electrical conversion efficiencies of up to 29.4 percent. In addition,
the modular design of dish/engine systems make them a good match for both remote
power needs, in the kilowatt range, as well as grid-connected utility applications in the
megawatt range.
System capital costs for these systems are presently about $4-5 per watt for parabolic
trough and power tower systems, and about $12-13 per watt for dish/engine systems.
However, future cost projections for trough technology are higher than those for power
towers and dish/engine systems due in large part to their lower solar concentration and
hence lower operating temperature and efficiency.
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“India has 2740 kW Grid connected systems (25-239 kw),Which
has Array Efficiency of 12% -15 % in Field, costs around Rs 26
crore/Megawatt or Rs. 15-20 /Kwh
Hydropower
5.1. Introduction
Hydropower is the largest renewable resource used for electricity. It plays an essential role
in many regions of the world with more than 150 countries generating hydroelectric
power. A survey in 1997 by The International Journal on Hydropower & Dams found that
hydro supplies at least 50 percent of national electricity production in 63 countries and at
least 90 percent in 23 countries. About 10 countries obtain essentially all their commercial
electricity from hydro, including Norway, several African nations, Bhutan and Paraguay.
There is about 700 GW of hydro capacity in operation worldwide, generating 2600
TWh/year (about 19 percent of the world’s electricity production). About half of this
capacity and generation is in Europe and North America with Europe the largest at 32
percent of total hydro use and North America at 23 percent of the total. However, this
proportion is declining as Asia and Latin America commission large amounts of new hydro
capacity.
Small, mini and micro hydro plants (usually defined as plants less than 10 MW, 2 MW and
100kW, respectively) also play a key role in many countries for rural electrification. An
estimated 300 million people in China, for example, depend on small hydro.
5.2. Capacity and Potential
There is vast unexploited potential worldwide for new hydro plants, particularly in the
developing countries of Asia, Latin America and Africa while most of the best sites have
already been developed in Europe and North America. There is also upgrading potential at
existing schemes though any future hydro projects will, in general, have to satisfy stricter
requirements both environmentally and economically than they have in the past.
As shown in Table 4 the world’s gross theoretical hydropower potential is about 40000
TWh/year, of which about 14000 TWh/year is technically feasible for development and
about 7000 TWh/year is currently economically feasible. The last figure fluctuates most
being influenced not only by hydro technology, but also by the changing competitiveness of
other energy/electricity options, the status of various laws, costs of imported
energy/electricity, etc.
As can be seen in Table 4 the biggest growth in hydro generation is expected in the
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developing countries where there is still a large potential for hydro development, while
relatively little growth is expected in most OECD countries where more than 65 percent of
the economic potential is already in use. Thus, at least in the near future, hydro will likely
remain the main source of electricity generation in developing countries that possess
adequate water resources.
Until recent years there has been less than 100 GW (about 350 TWh/year) of new hydro
capacity under construction at any one time, equivalent to less than 15 percent of the
capacity in operation. The figure has now risen, reflecting China’s vast construction
program, which includes the 18.2 GW Three Gorges Project, now in its second phase of
construction. Most new hydro capacity is under construction in Asia and South America.
China has by far the most, with about 50 GW under way. Brazil has largest resources in
world (800,000 GWh/year) ofeconomically exploitable capacity and Norway depends
almost entirely hydro for its electricity needs.
Hydropower continues to be the most efficient way to generate electricity. Modern hydro
turbines can convert as much as 90 percent of the available energy into electricity. The best
fossil fuel plants are only about 50 percent efficient. In the U.S., hydropower is produced for
an average of 0.7 cents/kWh. This is about one-third the cost of using fossil fuel or nuclear
and 1/6the cost of using natural gas. Hydro resources are also widely distributed compared
with fossil and nuclear fuels and can help provide energy independence for countries
without fossil fuel resources. There is also significant, widespread activity in developing
small, mini and micro hydro plants.
At least forty countries, particularly in Asia and Europe, have plants under construction
and even more have plants planned. China, Brazil, Canada, Turkey, Italy, Japan and Spain all
have plans for more than 100 MW of new capacity.
5.3. Small Hydro
Small-scale hydro is mainly ‘run of river,’ so does not involve the construction of large
dams and reservoirs. It also has the capacity to make a more immediate impact on the
replacement of fossil fuels since, unlike other sources of renewable energy, it can generally
produce some electricity on demand (at least at times of the year when an adequate flow of
water is available) with no need for storage or backup systems. It is also in many cases cost
competitive with fossil-fuel power stations, or for remote rural areas, diesel generated
power.
Small hydro has a large, and as yet untapped, potential in many parts of the world. It
depends largely on already proven and developed technology with scope for further
development and optimization. Least-cost hydro is generally high-head hydro since the
higher the head, the less the flow of water required for a given power level, and so smaller
and less costly equipment is needed. While this makes mountainous regions very attractive
sites they also tend to be in areas of low population density and thus low electricity
demand and long transmission distances often nullify the low cost advantage. Low-head
hydro oon the other hand is relatively common, and also tends to be found in or near
concentrations of population where there is a demand for electricity.
Unfortunately, the economics also tend to be less attractive unless there are policy
incentives in place to encourage their development.
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5.4. Environmental and Social Impacts
Although hydroelectricity is generally considered a clean energy source, it is not totally
devoid of greenhouse gas emissions (GHG) and it can often have significant adverse socio-
economic impacts. There are arguments now that large-scale dams actually do not reduce
overall GHG emissions when compared to fossil fuel power plant. To build a dam significant
amounts of land need to be flooded often in densely inhabited rural area, involving large
displacements of usually poor, indigenous peoples. Mitigating such social impacts
represents a significant cost to the project, which if it is even taken into consideration,
often not done in the past, can make the project economically and socially unviable.
Environmental concerns are also quite significant, as past experience has shown. This
includesreduction in biodiversity and fish populations, sedimentation that can greatly
reduce dam efficiency and destroy the river habitat, poor water quality, and the spread of
water-related diseases. In fact, in the U.S. several large power production dams are being
decommissioned due to their negative environmental impacts. Properly addressing these
issues would result in an enormous escalation of the overall costs for producing
hydropower making it far less competitive then is usually stated. As many countries move
toward an open electricity market this fact will come into play when decisions regarding
investments in new energy sources are being made. If the large hydro industry is to survive
it needs to come to grips with its poor record of both cost estimation and project
implementation.
5.5. Conclusions
Hydropower is a significant source of electricity worldwide and will likely continue to grow
Especially in the developing countries. While large dams have become much riskier
investment there still remains much unexploited potential for small hydro projects around
the world. It is expected that growth of hydroelectricity will continue but at a slower rate
than that of the 70’s and 80’s. Thus, the fraction of hydroelectricity in the portfolio of
primary sources of energy, which is today at 19 percent, is expected to decrease in the
future. Improvements and efficiency measures are needed in dam structures, turbines,
generators, substations, transmission lines, and environmental mitigation technology if
hydropower’s role as a clean renewable energy source is
to continue to be supported.
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Geothermal Energy
6.1. Introduction
Geothermal energy, the natural heat within the earth, arises from the ancient heat
remaining in the Earth's core, from friction where continental plates slide beneath each
other, and from the decay of radioactive elements that occur naturally in small amounts in
all rocks. For thousands of years, people have benefited from hot springs and steam vents,
using them for bathing, cooking, and heating. During this century, technological advances
have made it possible and economic to locate and drill into hydrothermal reservoirs, pipe
the steam or hot water to the surface, and use the heat directly (for space heating,
aquaculture, and industrial processes) or to convert the heat into electricity.
The amount of geothermal energy is enormous. Scientists estimate that just 1 percent of
the heat contained in just the uppermost 10 kilometers of the earth’s crust is equivalent to
500 times the energy contained in all of the earth's oil and gas resources. Yet, despite the
fact that this heat is present in practically inexhaustible quantities, it is unevenly
distributed, seldom concentrated and often at depths too great to be exploited industrially
and economically.
Geothermal energy has been produced commercially for 70 years for both electricity
generation and direct use. Its use has increased rapidly during the last three decades and
from 1975 – 1995 the growth rate for electricity generation worldwide has been about 9
percent per year and for direct use of geothermal energy it has been about 6 percent per
year. In 1997 geothermal resources had been identified in over 80 countries and there
were quantified records of geothermal utilization in at least 46 countries.
6.2. Capacity and Potential
Exploitable geothermal systems occur in a number of environments. High temperature
fields used for conventional power production occur mainly in areas of high geological
activity. Low temperature resources for direct heating can be found in most countries and
can now also be accessed using recently developed ground source heat pumps.
The worldwide use of geothermal energy amounts to about 44 TWh/year of electricity and
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38 TWh/year for direct use as shown in Table 5. While geothermal accounts for only about
0.3 percent of the total electrical power generated worldwide, amongst renewable sources
(excluding hydro) it ranks first at around 80 percent of the total. It is currently estimated
that the geothermal potential of the world for electricity production is 12,000 TWh/year
and for direct use it is estimated to be even larger at 600,000 EJ. A very small fraction of the
geothermal potential has therefore been developed so far, and an accelerated use of
geothermal energy in the near future is certainly feasible. In addition, the technology for
both electricity generation and direct application is mature and accessible. Thus, the
question of its future development depends upon whether it is economically competitive
with other energy sources in the different markets around the world.
6.3. Environmental Impacts
Geothermal fluids contain variable concentrations of gases, largely nitrogen and carbon
dioxide with some hydrogen sulphide and smaller proportions of ammonia, mercury, radon
and boron.
Most of these chemicals are concentrated in the disposal water which is usually reinjected
back into the drill holes so that there is minimal release into the environment. The
concentrations of the gases are usually low enough not to be harmful or else the abatement
of toxic gases can be managed with current technology.
Carbon dioxide is the major component of the noncondensible gases in the steam, but its
emission into the atmosphere per kWh is well below the figures for natural gas, oil, or coal-
fired power plants. Hydrogen sulphide is the pollutant of most major concern in
geothermal plants yet even the sulfur emitted with no controls is only half what is emitted
from a coal-fired plant.
Overall, with present technology able to control the environmental impact of geothermal
energy development, it is considered to be a relatively benign source of energy.
6.4. Conclusions
Geothermal as noted is not available everywhere especially with the resources required for
the production of electrical energy on an industrial scale. Nonetheless, geothermal energy
is generally cost competitive with conventional energy sources and is produced by well
proven conventional technology. It is reliable and has been used for the more than half of
the last century to heat large municipal districts, as well as to feed power plants generating
hundreds of megawatts of electricity. It has strong potential to continue to expand,
especially in the developing countries and is a clean energy source which can help
contribute to reducing our greenhouse gas emissions. It is felt that in the near-term the
future development of geothermal
could help fulfill a bridging function during the next few decades as other more modern
clean fuel technologies and renewables mature enough to provide a meaningful share of
the world energy supply.
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Renewable Energy System Cost and Performance
7.1. Recent progress in Renewable Energy System Cost and Performance
As previously described there has been significant progress in cost reduction made by wind
and PV systems, while biomass, geothermal, and solar thermal technologies are also
experiencing cost reductions, and these are forecast to continue. Figure 8 presents
forecasts made by the U.S.
Of course, capital costs are only one component of the total cost of generating electricity,
which also includes fuel costs, and operation and maintenance costs. In general, renewable
energy systems are characterized by low or no fuel costs, although operation and
maintenance (O&M) costs can be considerable. It is important to note, however, that O&M
costs for all new technologies are generally high, and can fall rapidly with increasing
familiarity and operational experience. Renewable energy systems such as photovoltaics
contain far fewer mechanically active parts than comparable fossil fuel combustion
systems, and therefore are likely in the longterm to be less costly to maintain.
Merrill Lynch's Robin Batchelorrecently stated:
“This is not an ethical investment opportunity, it's a straightforward business
opportunity.”
Mr. Batchelor also noted that the traditional energy sector has lacked appeal to investors in
recent years because of heavy regulation, low growth, and a tendency to be highly cyclical.
He has identified 300 companies worldwide whose aim is to develop wind, solar, and wave
power technologies and to advance capabilities in energy storage, conservation, and on-site
power generation.
Further evidence of the impending transition to renewable energy systems can be found in
recent corporate re-organization among the world’s largest oil companies. Corporate giants
such as Shell and BP/Amoco, which would now like to be known as “energy companies”
rather than “oil companies,” have recently re-organized into a broader array of business
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units, including those exclusively focused on renewables. Such subsidiary units now
include “Shell Renewables,” and “BP Solar.”
Conclusions
In conclusion, we believe that the promise of renewable energy has now become a reality.
Both solar photovoltaic and wind energy are experiencing rapid sales growth, declining
capital costs and costs of electricity generated, and continued performance increases.
Because of these developments, market opportunity exists now to both innovate and to
take advantage of emerging markets, with the additional assistance of governmental and
popular sentiment. The development and use of these sources can enhance diversity in
energy supply markets, contribute to securing long term sustainable energy supplies, make
a contribution to the reduction of local and global atmospheric emissions, provide
commercially attractive options to meet specific needs for energy services particularly in
developing countries and rural areas, and create new employment opportunities.
Integration of renewable energy supplies and technologies into the mix can help to temper
the cyclical nature of fossil fuel markets, and can give renewables a foothold from which
they can continue to grow and compete.
There are many opportunities for creative integration of renewables into energy
production systems. These include combined fossil and biomass-fueled turbines and
combinations of intermittent renewable systems and base-load conventional systems with
complementary capacity profiles. Strategies such as these, in conjunction with
development of off-grid renewable systems in remote areas, are likely to provide continued
sales growth for renewable and other CETs for many years to come.
At present, however, the rates and levels of investment in innovation for renewable and
other CETs are too low. This is the case because of market imperfection that undervalues
the social costs of energy production, the fact that firms cannot typically appropriate the
full value of their R&D investments in innovation, and because new technologies are always
characterized by uncertain performance and thus greater risk compared to their more
well-developed rivals. These issues suggest a role for public sector involvement in
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developing markets for renewable energy technologies through various forms of market
transformation programs.
Finally, we conclude that current energy producers are in the best position to capture new
renewable energy markets. These producers have the capital needed to make forays into
these markets, and the most to lose if they do not invest and renewable energy
technologies continue to flourish. We believe that artful introduction and integration of
renewable energy technologies into energy production systems, along with encouragement
from the public sector where appropriate, can provide a path that eventually leads to heavy
reliance on renewable energy systems in the future. This future would be more
environmentally and socially sustainable than one we would achieve by following a more
“conservative” path based on continued reliance on fossil fuels. This latter path in many
ways implies higher risks to human and ecological health and welfare over time, and it is a
path that is increasingly difficult to justify based on the performance that renewables are
now achieving
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